Split decision Experts differ over the long-term feasibility of having the world's largest telescope facility split over two continents.

The comments come in the wake of the recent decision to share the $2 billion telescope between Australia, New Zealand and South Africa.

Under the decision, announced on Friday, Australian facilities will be used for 'big picture' mapping of the universe, using low and medium frequencies in the radio spectrum.

These facilities include the Murchison Widefield Array that can focus on the very early universe and the Australian Square Kilometre Array Pathfinder that can focus on the more recent universe.

Meanwhile, South Africa facilities will be responsible for zooming in on, and taking a detailed look at, objects of interest discovered in the mapping process.

Nobel Prize winning astronomer Professor Brian Schmidt from the Australian National University agrees with the widely-reported Australian sentiment that the decision is a sensible compromise - but, he says, this is only likely to be the case in the short term.

"In the short term the decision has been a good one and I'm fully supportive of it. I would like to see more flexibility about what we do downstream," he says.

Schmidt says Phase 1 of the project, which will take five years, will be building on infrastructure that is already in existence in Australia.

"The extra cost of doing it compared to putting it in South Africa is almost nothing," he says.

But he says in Phase 2, facilities will need to be scaled up by a factor of 10 and the cost of additional infrastructure could threaten the viability of the telescope.

"I think it's probably going to be between 30 and 40 per cent more expensive [to keep split facilities] and that's a lot of money when you're talking billions of dollars," says Schmidt.

"I would hate to see the whole thing not be the best instrument it can be or potentially fail because we've decided to split the site and we just don't have enough money to build it then."

'Not a huge burden'

However Professor Peter Quinn, director of the International Centre for Radio Astronomy Research is less worried about the cost of having a split site.

He says while certain infrastructure will need to be scaled up, some of it is already good enough for the full blown telescope, such as the fibre optic NBN link that will service the facility.

"I personally don't think the split site is a huge burden. Maybe it's a 10 per cent or 15 per cent burden," says Quinn, who was involved in putting the Australian bid for the SKA together.

He says any extra cost will be made up for by the fact that split facilities will enable survey work to be done in Australia in parallel with deep field work being done in South Africa

Quinn says using multiple sites for observatories is "routine", citing, for example, the European Southern Observatory, which has telescopes at two sites in Chile and operations run from Munich.

Investment

Professor Bryan Gaensler of the University of Sydney says it would be a waste to abandon infrastructure that has been put in place in both places for the SKA.

And he says having the SKA in two places brings investment from all parties that far offsets the extra costs.

"So you have to choose. Do you put it in one place and not worry about the extra cost but lose all the investment money or do you wear the extra cost but get more investment," says Gaensler.

He says whatever happens in the longer term, the most recent decision was a smart move.

"They're keeping everyone engaged and making sure that the project is actually going to happen," says Gaensler.

"As a scientist it's not which country gets bragging rights but that we get a telescope that does what it was designed to do."

No matter where the final telescope ends up, Schmidt emphasises Australia's involvement should be equally strong.

"The interesting parts of the telescope are going to be made in Australia and shipped either to the middle of Western Australia or across the Indian Ocean," he says.